Fluid-operated servomechanism



United States Patent [72] Inventor George N. Bliss 8620 106th SE, Renton, Washington 98055 [21] Appl. No. 601,620

[22] Filed Dec. 14, 1966 [45] Patented Nov.3,1970

[54] FLUID-OPERATED SERVOMECHANISM 9 Claims, 2 Drawing Figs.

[52] U-S- Cl 91/51, 91/459, 92/131, 251/137, 251/141 [51] Int. Cl ..F16b 13/044, F161) 11/15 [50] Field ofSearch 91/47, 50, 51;92/131; 251/11 [56] References Cited UNITED STATES PATENTS 2,121,874 6/1938 Hodgkins 92/131 2,543,522 2/1951 Cohen .1 137/412X 2,922,401 1/1960 Hromas et a1 91/47 3,229,518 1/1966 Nilsson 137/412X FOREIGN PATENTS 874,370 5/1942 France 9l/51 907,473 3/1951 Germany.... 91/47 Primary Examiner-Carrol1 B. Dority, Jr. An0rneySeed and Berry ABSTRACT: The actuator of the present invention is of that; type in which a choked pressure supply of a liquid fluid is charged from a common source to the opposite sides of a normally centered shuttle-mounted governor piston, and by the activation of control means is caused to be bled from either side of the piston, selectively, at a rate of flow exceeding the charging rate so that a condition of differential pressure is created causing the piston to be shifted toward the side of lesser pressure.

This invention relates to actuators and particularly fluidoperated actuators of the servomechanism character.

FLUID-OPERATED SERVOMECHANISM OBJECTS OF THE INVENTION The general object of the present invention is to perfect an actuator of the above type by providing a positive-acting system of simple and comparatively inexpensive construction having a minimum number of moving parts, which is adapted or can be adapted to a wide range of applications, and which is reliable and extremely sensitive.

A further and particular object is to provide an actuator of the nature described having two independently operated valves which serve as the' control means, and for the operation of said valves employing respective solenoids so operatively interconnected with the valves and with flow-checking devices that (l) a selective excitation of the solenoids responsively shifts the piston in a respective one of two opposite directions, and (2) an activation of the other solenoid while the first said solenoid remains excited locks the piston in the particular position to which the same was shifted.

A yet further and particular object of the invention is to devise an actuator of the nature described in which the two valves, in applications where the same may be desirable, admit of being operated by mechanical means such as a pressure-applying lever, and wherein activating force may be applied to the lever either directly by hand or from a remote point as an automatic response reflecting a change in the physical-say temperature or pressure-characteristic of a control agent.

These and other more particular objects and advantages will appear and be understood in the course of the following description and claims, the invention consisting in the novel construction and in the adaptation and combination of parts hereinafter described and claimed.

DESCRlPTlON OF DRAWINGS In the accompanying drawings:

HO. 1 is a fragmentary, longitudinal, vertical, sectional view illustrating an actuator constructed in accord with the present invention and using solenoids as the governing controls; and

FIG. 2 is a fragmentary, longitudinal, vertical, sectional view of the valve portion of the actuator and illustrating a modified control system for the valves.

pled, the spindle moves in concert with the piston and, when uncoupled, moves independently thereof, thus to permit either remote control (using the above-mentioned mechanism hereinafter to be described) or local control (using the shift rod 22). Said detachable connection is made automatically and is provided by a set of balls 23 carried in pockets which are formed in the shaft 16, and forced outwardly into a surrounding groove of the header 13 or inwardly into a registering groove of the spindle 20, depending upon whether the spindle is moved relative to the shaft or the shaft moved relative to the header. With the balls lodged in the outer groove the shaft is perforce locked against movement. When lodged in the inner groove the shaft is locked to the spindle.

Piston 14 is movable against the yielding influence of v springs 23 from the centered position in which it is illustrated toward either of two terminal positions located at the opposite end limits of the pistons permitted slide travel. Two spring keepers 24 and 25, held in place by split rings, act to normally center the piston. The keepers are perforated so that fluid can freely pass.

Each of the two headers is vertically elongated to produce upwardly extending chest sections 26 and 27, and fluid from a reservoir 28 is fed under the pressure influence ofa common pump 30 through connections 31 and 32 to the inlet ends of flow passages 33 and 34 which are formed in the chests. Received in the inlet ends are respective fittings, as 35 and 36, providing seats for spring-pressed check valves 37 and 38 closing against the pressure of the supplied fluid. The springs are quite light in that the check valves are caused to close only when the oil within the chest is in a static condition, reflecting DESCRIPTION OF lNVENTlON Referring to said drawings, the numeral 10 denotes a sleeve secured by stayrods 11 between two headers 12-13 and serving as the cylinder for a shuttle-type piston 14. A circumferential groove in the pittton receives a sealing O-ring 15. The piston in cntrictl upon the median portion of n center-bored shaft 16, being held against endwise displacement thereon. The shaft is journaled for endwise motion in the headers, and protrudes by both ends therefrom. O-rings are employed to seal the journaled ends of the shafts and sealing O-rings are also provided at the ends of the sleeve 10.

By force of fluid pressure applied to either side of the piston, selectively, and made to respond in a manner hereinafter described either to a manually or automatically governed control means which are or may be located remote to the piston, the piston serves, by its shuttle movement, as an actuator for axially moving the stem 17 of a control member (not shown) so as to shift the member from a normal centered neutral position to and from either of two operating positions. By way of example, the member is or may be applied to control the delivery of hydraulic fluid to the two sides of a reversible hydraulic motor.

Connection from the piston 14 to the stem 17 is afforded by a spindle 20 which receives a sliding fit in the hollow center of the shaft 16. Both ends of the spindle project beyond the shaft. The inner end has an adapter nut 21 threaded thereon and the stem 17 is hooked to the adapter nut. A manual shift rod 22 threads into the outer end. A detachable connection is provitletl between Illc spindle "ml the shaft In no that, when con-- the closing of an exhaust port hereinafter to be described. Each chest is bored to provide a lower and an upper side port, as 40-41 and 42-43. The lower ports 40 and 42 each connect the respective flow passage with a related end of the cylinder. The upper ports 41 and 43 each lead to a respective one of two facing coaxial sockets. Suitably sealed by O-rin'gs, the two ends of a crosstube are fitted in these sockets. End portions of the tube each function as the mounting core for a respective one oftwo solenoids 44 and 45. A respectiveone of two cylindrical dump valves 46 and 47 forms the armature for each solenoid, with excitation of the solenoids urging the armatures directively from one another, and which is to say outwardly from a centrally located radial discharge passage 48 which dumps through a connection 49 to the reservoir 28. The crosstube is comprised of two coaxial sections 50 and 51 threaded by their inner ends in a collar 52. The radial discharge passage is formed in the collar.

The dump valves 46 and 47 each have a solid-tipped'conical nose 53 which closes off the related end ofthe crosstubc's hollow center by being brought to bear against a valve ttent. Beyond the solid tip are ports 54 extending radially of the valve from its conical surface to a rear center-bore 55. Fluid entering the center-bore perforce escapes through the dump passage 48. It is desirable that the flow capacity of the inlet openings through which fluid enters the flow passages 33 and 34 be somewhat choked.

Electric circuits for the two solenoids each include a respective one of two circuit-closing switches 56 and 57"loc'ated remote to the actuator. When the valve-forming armatures are seated, the conical nose lies at'the substantial center, longitudinally considered, of the related coil so as to be then subject to the coil s maximum pull force.

The present invention accomplishes its greatest usefulness, and is intended to be applied, in activating a coritrol member such as a valving spool which requires arrestation at any selected position, i.e.- either at full-over forward, full-over reverse, or any desired point between a centered neutral loca-' operator now excite the other solenoid at any stage of such piston travel, while continuing to excite the first-acting solenoid, the piston is instantly arrested in that the previously open escape route is closed and both check valves responsively seat to isolate the two ends of the cylinder from the pressure lines 31 and 32. The differential pressures to which the piston was subject become locked-in" until one or both solenoids are dccncrgized. In the absence of the check valves the pressures would perforce balance out through the pressure lines 31 and 32 in that the source pressure is the same for both lines.

With the dump valves 46 and 47 open there is a continuous flow of oil. In consequence of directing this oil through a passageway formed within the solenoids the oil performs a cooling function upon the solenoids by dissipating heat therefrom.

With reference being now had to FIG. 2, a mechanical means is provided for sliding the dump valves 46 and 47 within the bore of the crosstube. Comprised of a rocking lever 60 having the free end of its work arm received between said valves so as, by swing motion in either of two opposite directions about a fulcrum 61, to bring either the valve 46 or the valve 47 against its seat, the activation of the lever may be performed either manually or, as here shown, automatically in response to a given condition or conditions. As one example of applicable usage, the actuator can be advantageously employed as an auto pilot for a marine vessel, in which usage it is to be assumed that the spindle is made a part of the steering system and causes the rudder to reflect endwise motions of the piston 14 as the latter moves in opposite directions from center. in the arrangement here illustrated the lever 60 is of the third order. lts power arm 62 is operated by two pressureresponsive diaphragms 63 and 64 which connect by pipes 65 and 66 with a respective one of two spaced-apart gas (or liquid) bulbs 67 and 68; intervening between the bulbs is a constantly energized heating element 70 and two screening cards 71 and 72. The cards move in concert in either of two opposite directions from a normal centered position at which an identical portion of both bulbs are exposed to the radiated heat of the element. The screening cards respond to movements of an adjustable compass card. For any movement of the vessel off-course from a selected setting, the bulbs become subjected to differing degrees of heat exposure and this difference, creating a corresponding pressure differential between the forces of opposition imposed by the diaphragms upon the power arm of the lever, moves the latter to close the particular dump valve necessary in order to responsively shift the piston in the direction required to obtain a compensating swing of the vessel's rudder. A case 73 houses the diaphragms 63 and 64. The dumped oil is or may be directed through the case in its discharge to the reservoir.

lt will be apparent that the volumetric rate at which the pumped oil flows into the two chests 26 and 27 determines the speed at which the piston 14 responds. The fittings 35 and 36 determine the flowrate, and this rate may be regulated either by changing one for another fitting or by using a fitting (not shown) which has a means such as a needle valve for varying the flow capacity of its orifice.

In respect of the shadow amplifying system which I have shown in FIG. 2, it will be seen that there is provided a control means needing no physical contact. The radiant energy is used to sense the position of an object or objects and with this energy shielded there is no reaction on even the most sensitive gage or other dial.

I claim:

1. An actuator for shifting a member in either of two opposite directions from center, comprising: a closed cylinder having a respective admission port leading to each of the two ends; a piston mounted for shuttle movement within the cylinder; spring means normally centering the piston within the cylinder; a pressure source of fluid supply connected with each of the admission ports; a respective passageway communicating with each end of the cylinder and through which fluid is dumped; and independently operated respective valve elements for opening and closing said passageways, the passageways when open having a volumetric flow capacity exceeding the volumetric flow capacity of the admission ports so that by closing one and opening the other valve element a piston-shuttling imbalance can be produced between the pres" sure obtaining in the cylinder at one side and that obtaining in the cylinder at the other side of the piston, the valve elements being each solenoid-operated with each valve element normally open and upon an energizing of the related solenoid caused to close against the pressure which obtains in the cylinder, each of said passageways extending centrally through the coil of the solenoid which is related to the concerned valve element, the valve element being the armature for the coil.

2. An actuator as claimed in claim 1 in which a reservoir is provided from which the pressure source draws fluid and characterized in that dumped fluid returns to the reservoir and in its traversal of either passageway flows axially through the related solenoid.

3. An actuator as claimed in claim 1, the passageways being in communicating coaxial relation and having valve seats at the two ends and a common dump opening at the center, a respective one of the valve elements being received for slide movement in each end of said passageway to close upon a related one of the seats against the pressure which obtains in the cylinder.

4. An actuator as claimed in claim 3, the armature-forming valve element, when closed, locating its seating end at the substantial longitudinal center of the coil.

5. An actuator for shifting a member in either of two opposite directions from center, comprising: a closed cylinder having a respective admission port leading to each of the two ends; a piston mounted for shuttle movement within the cylinder; spring means normally centering the piston within the cylinder; a pressure source of fluid supply connected with each of the admission ports; a respective passageway communicating with each end of the cylinder and through which fluid is dumped; and independently operated respective valve elements for opening and closing said passageways, the passageways when open having a volumetric flow capacity exceeding the volumetric flow capacity of the admission ports so that by closing one and opening the other valve element a piston-shuttling imbalance can be produced between the pressure obtaining in the cylinder at one side and that obtaining in the cylinder at the other side of the piston, said valve elements being each solenoid-operated with each valve element being normally open and upon energizing of the related solenoid closing against the pressure which obtains in the cylinder, said actuator having a respective check valve for each admission port urged into a closed position against the pressure of the supplied fluid by springs exerting a force inferior to said supply pressure.

6. An actuator for shifting a member in either of two opposite directions from center, comprising: a closed cylinder having a respective admission port leading to each of the two ends; a piston mounted for shuttle movement within the cylinder; spring means normally centering the piston within the cylinder; a pressure source of fluid supply connected with each of the admission ports; a respective passageway communicating with each end of the cylinder and through which fluid is dumped; and independently operated respective valve elements for opening and closing said passageways, the passageway when open having a volumetric flow capacity exceeding the volumetric flow capacity of the admission ports so that by closing one and opening the other valve element a piston-shuttling imbalance can be produced between the pressure obtaining in the cylinder at one side and that obtaining in the cylinder at the other side of the piston, said passageways being in communicating coaxial relation and having valve seats at the two ends and a common dump opening at the center, a respective one of the valve elements being received for slide movement in each end of said passageway to close upon a related one of the seats against the pressure which obtains in the cylinder. the operation of closing the valve elements being performed mechanically by a common lever element extending into the passageway through the dump openmg.

7. An actuator as claimed in claim 6 having a pressureresponsive means for operating the lever element.

8. An actuator for shifting a member in either of two opposite directions from center, comprising: a closed cylinder having a respective admission port leading to each of the two ends; a piston mounted for shuttle movement within the cylinder; spring means normally centering the piston within the cylinder; a pressure source of fluid supply connected with each of the admission ports; a respective passageway communicating with each end of the cylinder and through which fluid is dumped; and independently operated respective valve elements for opening and closing said passageways, the passageways when open having a volumetric flow capacity exceeding the volumetric flow capacity of the admission ports so that by closing one and opening the other valve element a piston-shuttling imbalance can be produced between the pressure obtaining in the cylinder at one side and that obtaining in the cylinder at the other side of the piston, the actuator having a center-bored shaft to which the piston is fixedly journaled for endwise sliding movement in the end walls of the cylinder, and having a shift spindle which admits of being moved by hand and which is journaled for endwise sliding movement in the center-bore of the shaft, means being provided for either coupling the spindle to the shaft so that the spindle is made to respond to said imbalance of pressures within the cylinder or uncoupling the spindle from the shaft while at the same time immobilizing the shaft so that movement of the spindle is made a hand operation.

9. An actuator as claimed in claim 8 in which applications of force applied when the shaft and the spindle occupy a centered position and either to the spindle by hand or to the shaft in response to said imbalance of pressures acts automatically in the respective instance to uncouple the spindle while immobilizing the shaft or to couple the spindle to the shaft. 

